As rotation transmission devices configured to selectively perform and stop the transmission of the rotation of a driving shaft to a driven shaft, rotation transmission devices are known which include a two-way clutch, and an electromagnetic clutch configured to selectively engage and disengage the two-way clutch.
Japanese Unexamined Patent Application Publication No. 2009-293679 discloses a rotation transmission device including an outer ring having a cylindrical surface on its inner periphery, an inner ring having cam surfaces on its outer periphery, and provided inside of the outer ring, a control retainer and a rotary retainer provided between the outer ring and the inner ring such that pillars of the control retainer circumferentially alternate with pillars of the rotary retainer, opposed pairs of rollers received in pockets defined between adjacent ones of the pillars of the control retainer and the pillars of the rotary retainer, and elastic members received between the respective opposed pairs of rollers. The opposed pairs of rollers are biased away from each other by the corresponding elastic member so as to be kept at a standby position at which the rollers engage with the cylindrical surface of the outer ring and the corresponding cam surface of the inner ring. When the inner ring rotates in one direction, one of each opposed pair of rollers engage with the cylindrical surface and the corresponding cam surface so as to transmit the rotation of the inner ring to the outer ring.
The rotation transmission device of Japanese Publication No. 2009-293679 further includes an input shaft connected to the inner ring, and an electromagnetic clutch having an electromagnetic coil, and provided on the input shaft. When the electromagnetic coil of the electromagnetic clutch is energized, the control retainer axially moves. As a result thereof, due to a torque cam provided between the opposed surfaces of a flange of the control retainer and a flange of the rotary retainer, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the respective pockets decrease, so that the pairs of rollers are moved to their disengaged position by the pillars of the control retainer and the respective pillars of the rotary retainer, thereby stopping the transmission of the rotation of the inner ring to the outer ring.
In the above rotation transmission device, when the electromagnetic coil of the electromagnetic clutch is de-energized, due to the pressing force of the elastic members received between the respective opposed pairs of rollers, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the respective pockets increase, thereby moving the respective opposed pairs of rollers to the standby position at which the pairs of rollers abut the cylindrical surface and the respective cam surfaces. Therefore, when the inner ring rotates, the pairs of rollers instantly engage with the cylindrical surface and the respective cam surfaces, namely, the rollers scarcely move in the rotational direction, and can respond quickly.
In the rotation transmission device disclosed in Japanese Publication No. 2009-293679, with the electromagnetic coil of the electromagnetic clutch is de-energized, the opposed pairs of rollers move toward the standby position at which the rollers abut the cylindrical surface of the outer ring and the respective cam surfaces of the inner ring. When the outer ring and the inner ring rotate relative to each other, the rollers engage. With the rollers moved at the standby position or engaged, if disturbance such as vibration is applied to the rotation transmission device, the outer ring and the control retainer may rotate relative to each other due to moment of inertia. If the outer ring and the control retainer rotate relative to each other, one of each pair of rollers moves to its neutral position, so that torque cannot be transmitted between the outer ring and the inner ring. Therefore, there are some points which need to be improved so as to enable the rotation transmission device to operate with high reliability.
It is an object of the present invention to prevent rollers from moving to their neutral position due to disturbance with a two-way clutch engaged so as to enable a rotation transmission device to operate with high reliability.